1. Field of the Invention
This invention relates generally to the gear arrangement and shift mechanism for an automotive vehicle transmission, and especially to a transaxle transmission mechanism wherein a common axis of the engine and transmission is transversely disposed with respect to the fore-and-aft axis of the vehicle.
2. Description of the Prior Art
In general, a multiple speed ratio, manual transmission that provides five forward speed ratios will require a longer axial dimension than a transmission having four speed ratios. In front wheel drive road vehicles it is necessary that the transmission have a minimum axial dimension because of the restricted space available in the transverse direction into which the engine and transaxle must be fitted.
The transmission according to this invention permits a substantial reduction in the longitudinal dimension of the transmission. This advantage is realized because the mechanism includes, in addition to the input shaft, two countershafts. The first countershaft carries the four lower speed ratio gears, the second countershaft carries only the fifth speed ratio gear. The second countershaft transmits power only in the fifth speed ratio, therefore, the gear arrangement for a four speed ratio transaxle can be derived from the gear arrangement of the five speed transmission by simply removing the auxiliary countershaft assembly and the fifth speed ratio shift mechanism that actuates the synchronizer on the second countershaft.
In the prior art where multiple countershafts are employed in a transmission of this type, each countershaft transmits power for at least two of the speed ratios in which the transmission may function. Such an arrangement is not adaptable to function with a lesser number of speed ratios upon the removal of one countershaft and the shift mechanism that operates to driveably connect the pinions to the countershaft on which they are journalled.
The shift mechanism that controls the operation of the transaxle according to this invention is so designed that the four lower speed ratios and the reverse drive can be selected without affecting that portion of the shift mechanism that controls the operation of the fifth speed ratio.